Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$160.61	4.326%	$167.558	$167.56	$167.55	$167.60
Purchase #2	$13.30	4.508%	$13.8996	$13.90	$13.90	$13.90
Purchase #3	$84.83	7.223%	$90.9573	$90.96	$90.95	$91.00
Purchase #4	$171.82	9.818%	$188.6893	$188.69	$188.70	$188.70
Purchase #5	$59.49	6.253%	$63.2099	$63.21	$63.20	$63.20
Purchase #6	$243.32	8.391%	$263.737	$263.74	$263.75	$263.70
Purchase #7	$64.48	11.672%	$72.0061	$72.01	$72.00	$72.00
7 purchase totals =	$797.85		$860.0572	$860.07	$860.05	$860.10